Abstract
The messenger RNAs of the rice seed storage proteins prolamine and glutelin are targeted to distinct sub-domains of the cortical endoplasmic reticulum via a pathway dependent on both RNA sorting signals and the cytoskeleton. This RNA transport mechanism directly influences the final site of storage protein accumulation, with prolamines remaining within the ER lumen in spherical protein bodies while glutelins are exported to irregularly-shaped protein storage vacuoles. Developing rice seeds therefore represent a leading model for the study of RNA localisation in plants. Previous work using RNA affinity capture from cytoskeleton-enriched developing rice seed extracts has led to the identification of eighteen candidate prolamine RNA binding proteins (RBPs). Of these, RBP-A is a promising candidate for further study since its expression profile, intracellular localisation and in vivo RNA binding specificity all support a direct role for this protein in storage protein gene expression. Recently, mouse antibodies against RBP-A and a second promising candidate, RBP-D, have been generated and co-localisation data will be presented for these two proteins.
